A few years ago, frustrated by overcrowding on the London Underground and the cost of taxis, I decided to get some exercise and buy a bike. I hadnt cycled for years and had never previously owned a bike helmet. Spurred on by national advertising campaigns and the experiences of friends, I promised myself I would never cycle to work without adequately protecting my head. Fortunately for me, this was one promise I didnt break.

I went to a local bike shop to buy all the gubbins Id need for my new mode of travel. As a novice, I didnt know what I was looking for, so I told the assistant my price range and asked him to give me a few hints. After buying lights and reflective gear, it was time to select a bike helmet. This was fairly simple – the assistant measured my head and pointed to two or three that would fit, explaining the difference between each of them. I chose the one that looked the least ridiculous.

My helmet is made by Giro. It cost about £40 and could well have saved my life. For two years I travelled to work without major incident, although there were one or two near misses along the way. I have always been a cautious cyclist – I dont weave through traffic, I dont jump red lights. Yet when I changed from working nights to a day job last year, I found getting to work in heavy traffic a lot more difficult and extremely stressful.

One morning, I was cycling at full pelt along a bus lane and pulled out to overtake a car that was illegally parked. I didnt notice that its owner was still inside. By the time she opened the door, it was too late for me to brake or swerve. I slammed into the door, flew over my handlebars and bounced off a stationary car in the lane to my right, coming to a somewhat inelegant landing on the uneven tarmac.

My recollection of events is understandably blurry. But my one over-riding memory was thinking, as the back of my head bounced on the road, "That would really have hurt if I wasnt wearing a helmet.

In fact, other than a few bruised ribs, some grazes and a bent front wheel, no major damage was done at all. Some kind drivers and a shopkeeper helped me to the roadside and dragged my scuffed and twisted bike onto the pavement for me. As I gradually regained my breath and sipped at the obligatory cup of tea, I speculated as to what might have happened had I not been wearing a helmet.

I knew I had fallen backwards onto the ground at some momentum. I knew my head had hit with considerable force. Would I have cut or grazed it? Sustained mild concussion? Severe brain damage? Could it have been fatal?

Fortunately, Ill never know.

JAMES CURTIS